Unit 5 Chemical Compounds Chapter 6
Objective 1 ď Ž
Describe the three types of chemical bonds.
There are three types of bonds:
Ionic Covalent Metallic
Bonding
How can you tell what type of bond is going to form? You use what is called an electronegativity table. Electronegativity- is the tendency for an atom to attract a shared pair of electrons.
Objective 2 Use electronegatitivity differences to determine the chemical bond that will form.
Elements LI-Cl C-H H-H N-H C-H K-Br Na-S
EN
Difference I or C?
Elements P-H I-I Mg-Cl C-O O-O S-Cl N-N Na-Cl
EN
Difference I or C?
Electronegativity Difference Covalent 0
<
Ionic 1.67
Objective 3 Recognize stable electron configurations.
Ionic Bonding
All elements combine to obtain a stable electron configuration. Metals will lose electrons. Nonmetals will gain electrons.
Li-Cl
Lithium is 1s22s1. If lithium could lose one electron it would be like the noble gas helium. Chlorine is 1s22s22p63s23p5. When lithium loses it’s one electron it gives it to chlorine.
Li-Cl
So lithium will form a positive ion or cation with a charge of +1. When chlorine receives the one electron it will form a negative ion or anion with a charge of –1. The attraction of the oppositely charged ions will then form the compound LiCl, lithium chloride.
Li-Cl ď Ž
We can represent this with what is called a dot diagram.
Combining Atoms Lithium + Chlorine
ď&#x192;
Compound formed Lithium chloride
You teacher will draw this on the board. Copy!!
K-Br Potassium
+
Bromine
ď&#x192;
Potassium bromide
Mg-Cl Magnesium
+
Chlorine
ď&#x192;
Magnesium chloride
Na-Cl Sodium
+
Chlorine ď&#x192;
Sodium chloride
Objective 4 Describe how an ionic bond forms and how ionization energy affects the process.
Conclusions: ď Ž
ď Ž
Ionic bonding involves the transfer of one or more electrons from the metal to a nonmetal. Energy changes are involved. a.
b.
ď Ž
Ionization energy-the amount of energy needed to remove an electron from an atom. Electron affinity-the energy change when an electron is added.
The element that loses electrons will form a positive ion. +1, +2, +3 for example.
Conclusions, cont. ď Ž
ď Ž
ď Ž
The alkali metals, alkaline earth metals and aluminum will form positive ions equal to the group number. The element that receives the transferred electron(s) will form a negative ion. -1, -2 or -3 for example. The attraction of these oppositely charged ions is what forms the ionic bond and a compound has been formed.
Properties of Ionic Compounds 1. 2. 3.
4.
High melting point. Nonconductor in the solid state. Conductor when melted or dissolved in solution. Ionic compounds are electrolytesconductors of electricity in aqueous solution. Brittle, or shatter when hit with a hammer.
Objective 5 Recognize and describe binary ionic compounds, metals with multiple ions, and polyatomic ions.
Ionic Compounds
Binary compounds -a compound made from only two elements. Look at your List of Common Ions. An ionic compound can be made from any positive ion from the front combined with any negative ion on the back.
Ionic Compounds Li+
I-
The charges in a compound must be neutral. With +1 and â&#x20AC;&#x201C;1 we will need one of each. The formula is LiI.
Ionic Compounds Li+
ClO3- ClO2LiClO3
LiClO2
Ionic Compounds Li+ C2O4-2
Formula
need 2
need 1
Li2C2O4
need 1
Li2SO3
+2 -2 SO3-2 need 2 PO4-3 need 3 +3 -3
need 1 Li3PO4
Ionic Compounds Cr+2
Ineed 2
CrI2
ClO3Need 1 +2
need 2 -2
Cr(ClO3)2
Must use parenthesis on polyatomic ion.
Ionic Compounds Cr+2 C2O4-2 need 1 need 1 CrC2O4 SO3-2 need 1 need 1 CrSO3 PO4-3 need 3 need 2 Cr3(PO4)2 +6 -6 Be sure to use parenthesis.
Ionic Bonding ď Ž
Continue to complete the rest of the chart and check your work on the slides that follow.
KI
KClO3 KClO2 K2C2O4 K2SO3 K3PO4 no parenthesis when there is just one.
AlI3 Al(ClO3)3 Al(ClO2)3 Al2(C2O4)3 Al2(SO3)3 AlPO4
ZnI2 Zn(ClO3)2 Zn(ClO2)2 ZnC2O4 ZnSO3 Zn3(PO4)2
Lab Ionic Compounds. ď Ž
Use the foam ion cutouts to help you to write the formula for the ionic compounds.
Objective 6 Predict the composition of an ionic compound from its name.
Letâ&#x20AC;&#x2122;s name the compounds we made in Table 2.
Rules for Naming 1. 2.
3.
Name the positive ion first. If the positive ion has more than one charge, use a Roman numeral in the name. For example there is Cr+2 and Cr+3. So you have chromium (II) and chromium (III). Name the negative ion second.
Table 2 1. 2. 3. 4. 5. 6.
Lithium iodide Lithium chlorate Lithium chlorite Lithium oxalate Lithium sulfite Lithium phosphate
Table 2 Use Roman numeral with metals that have more than one charge. Chromium (II) iodide Chromium (II) chlorate Chromium (II) chlorite Chromium (II) oxalate Chromium (II) sulfite Chromium (II) phosphate
Table 2
Aluminum iodide Aluminum chlorate Aluminum chlorite Aluminum oxalate Aluminum sulfite Aluminum phosphate
Table 2
Zinc iodide Zinc chlorate Zinc chlorite Zinc oxalate Zinc sulfite Zinc phosphate
Table 2
Potassium iodide Potassium chlorate Potassium chlorite Potassium oxalate Potassium sulfite Potassium phosphate
Given the name, write the formula 1. 2. 3. 4. 5.
Copper (I) chloride Copper (II) chloride Calcium hydroxide Calcium carbonate Ammonium sulfate
2.
CuCl CuCl2
3.
Ca(OH)2
4.
CaCO3
5.
(NH4)2SO4
1.
Given the name, write the formula 6. 7. 8. 9. 10.
Silver sulfate Lithium fluoride Iron (II) sulfate Sodium oxide Sodium nitride
6.
Ag2SO4
7. 8.
LiF FeSO4
9.
Na2O
10.
Na3N
Assign WS I. Name the compounds in your Lab Ionic Compounds on the back of WS I.
Objective 7 ď Ž
Describe how covalent bonds form and the attractions that keep atoms together in molecules.
Table 1, slide 6
C-H In covalent bonding there is the sharing of one or more electron pairs. There is NO ELECTRON TRANSFER! The compound that forms stays together because the atoms that are bonding share the electrons to help obtain a stable electron configuration.
C-H
Carbon is 1s2 2s2 2p2 it has four valence electrons. Hydrogen is 1s1 and has one valence electron. Notice that if you put them together to make CH4, carbon will have 8 electrons around it and is stable and each hydrogen will have one pair. That fills the 1s level for hydrogen and it too is stable. Continue with the remaining covalent examples.
CH4 Dot Diagram
Polar bond Polar molecule
H2
Nonpolar bond Nonpolar molecule
NH3
Polar bond Polar molecule
Na2S
Ionic, not covalent. It is an exception. Draw showing electron transfer.
PH3
Polar bond Polar molecule
I2
Nonpolar bond Nonpolar molecule
CO
Polar bond Nonpolar molecule
CO2
Polar bond Nonpolar molecule Note: two double bonds formed
O2
Nonpolar bond Nonpolar molecule Double bond
SCl2
Polar bond Polar molecule
N2
Nonpolar bond Nonpolar molecule Triple bond
Terms:
A nonpolar bond is between like atoms. A polar bond is between different atoms. A nonpolar molecule results when the same element is around the compound. A polar molecule forms when the compound has “sides” or appears to be different all the way around.
Covalent Bonds
Single bond- the sharing of one electron pair. Double bond- the sharing of two electron pairs. Triple bond- the sharing of three electron pairs. Covalent bonds occur to help each element attain an octet
C2H6
Polar bond Nonpolar molecule
C2H4
Polar bond Nonpolar molecule Double bond
C2H2
Polar bond Nonpolar molecule Triple bond
Lab Covalent Compounds. ď Ž
Use the bag of atoms and plastic dots to help you to form the covalent compounds.
Objective 9 ď Ž
Name and determine the chemical formulas for molecular compounds.
Naming Covalent Compounds.
Typically covalent compounds are composed of two or more nonmetals combined. To name the compound, say the name of the first element and use Greek prefixes to indicate how many of each element you have. The second element ends in –ide.
The Greek prefixes are: 1 2 3 4 5
MonoDiTriTetraPenta-
6 7 8 9 10
hexaHeptaOctaNonaDeca-
Greek prefixes Never use mono on the first word, always use mono on the second! Compound Name CO carbon monoxide CO2 carbon dioxide ď Ž
SO2 sulfur dioxide N2H4 dinitrogen tetrahydride SO3 sulfur trioxide P2O5 diphosphorus pentoxide (drop the a in penta)
You try: N2O3 PCl3 SiO2 CCl4 I2O7 BeH2
Answers Dinitrogen trioxide Phosphorus trichloride Silicon dioxide Carbon tetrachloride Diiodine heptoxide (drop the a) Beryllium hydride
Properties of Covalent Compounds 1. 2. 3.
ď Ž
Low melting point. Formed by the sharing of electron pairs. Nonconductor in the solid state, when dissolved in water or when melted. Covalent compounds are non-electrolytes. Volatile (have an odor or forms fumes). Example: Isopropyl alcohol (rubbing alcohol), mothballs.
Objective 10 ď Ž
Describe the structure of bonds in metals.
Metallic Bonding
Metal atoms achieve stable electron configurations by losing electrons. But what happens if there are no nonmetal atoms available to accept the electrons? The metal atoms become cations surrounded by a “pool of shared electrons.”
Metallic Bonding
A metallic bond is created by the attraction between the positive metal cation to the electrons lost. These electrons are often referred to as “delocalized electrons.” The metal is still neutral in charge, in effect, because the number of protons and electrons are still equal.
Metallic Bonding
Objective 11 ď Ž
Relate the properties of metals to their structure.
Properties of Metals 1. 2. 3. 4.
Conductor of electricity and heat. Ductile Malleable Luster
Objective 12 ď Ž
Distinguish between ionic, covalent and metallic bonding. How the bonds are formed, the forces that hold them together and properties.
Summary: Types of Bonds
Ionic
Metal and nonmetal Large electronegativity difference > 1.67 Forms fomula units Transfer of electrons held together by electrostatic attraction
Properties of Ionic Compounds
Solids are nonconductors Liquids, gases and aqueous solutions are conductors. They are electrolytes High melting point and boiling point Low volatility Low vapor pressure
Summary: Types of Bonds
Covalent
Two nonmetals combined Small electronegativity difference < 1.67 Forms molecules Sharing of one or more electron pairs
Properties of Covalent Compounds
Noncoductors of electricity Non-electrolytes Low melting and boiling points Volatile High vapor pressure
Summary: Types of Bonds
Metallic
Composed of metal atoms Delocalized electrons are free electrons among the cations Electron Sea Model
Properties of Metallic bonding
Conductors of heat and electricity High melting and boiling point Malleable Ductile Luster
The end.